// 双指针
var maxProfit = function (prices) {
    var minPrice = prices[0], maxProfit = 0;
    for (var i = 0; i <= prices.length; i++) {
        // 最低点
        if (prices[i] < minPrice) {
            minPrice = prices[i] // 最低点
        } else if (prices[i] - minPrice > maxProfit) { // 可以卖出 
            maxProfit = prices[i] - minPrice
        }
    }
    return maxProfit
}

console.time()
console.log(maxProfit([7, 1, 5, 3, 6, 4]));
console.timeEnd()